An exemplary field of use of a magnetoinductive flow meter of this type can encompass the measurement of the flow rate of liquids, slurries and pastes which have a specific minimum electrical conductivity, for example. An exemplary type of flow-measuring device according to the subject matter of the disclosure is distinguished by very accurate measurement results, with the measurement not creating any loss in pressure in the pipeline system containing the flow-measuring device. In addition, magnetoinductive flow meters do not have any movable components or components which project into the measurement tube, which components would be subject to wear.
On account of the above-described device properties, magnetoinductive flow meters of this type can be used for product generation in the chemical industry, in the pharmaceutical and chemical industries, in water supply and distribution, in wastewater management, in the food industry and the like.
The physical basis for the measurement method used by a magnetoinductive flow meter is formed by Faraday's law of induction, which states that a voltage is induced in a conductor moving in a magnetic field. When utilizing this law of nature for measurement purposes, the electrically conductive medium flows through a measuring tube in which a magnetic field is produced substantially perpendicular to the direction of flow. The voltage induced in the medium is tapped off by an electrode arrangement. Since the measurement voltage obtained in this way is proportional to the determined flow rate of the flowing medium, the volumetric flow rate of the medium can be determined from this, taking into account the concentration and the mass flow rate.
DE 10 2004 053 065 A1 discloses a magnetoinductive flow meter of the generic type. This magnetoinductive flow meter substantially comprises a metal measuring tube which is incorporated in a pipeline via flanged portions at the ends. Two opposing measuring electrodes are inserted into the wall of the measuring tube in an electrically insulated manner. The measuring electrodes serve to detect a measurement voltage. An electromagnet unit, which is likewise arranged on the outside of the measuring tube, produces a magnetic field which is oriented substantially perpendicular to the direction of flow of the conductive measuring medium to be measured. The metal measuring tube has an insulating lining, which also extends over the flanged portions, for the purpose of electrical insulation.
EP 0 770 856 B1 discloses the structural design of an electromagnet unit of a magnetoinductive flow meter which is of interest within the scope of the present disclosure. This electromagnet unit has two electric coils which are positioned opposite one another on the measuring tube coaxially along the longitudinal axis. The coil arrangement produces the magnetic field with the desired orientation. In order to intensify the magnetic field oriented in this way, magnetic flux-concentrating means are used which interact with the inner pole cores of the electric coils, which are composed of a conventional coil former around which coil wire is wound. In the direction of the measuring tube, the end of the pole core is connected to a ferromagnetic plate which comes to rest on the measuring tube. The opposite end of the pole core is surrounded by a pot-like magnet yoke which, in the edge region, is mounted on iron rings which surround the measuring tube to close the magnetic circuit with the opposite electric coil.
The electromagnet unit formed in this way is surrounded by a separate non-magnetic housing which can be composed of stainless steel, for example.
One disadvantage of this conventional electromagnet unit has proven to be the large number of individual components of the magnetic flux-concentrating means which have to be fitted to one another. Since most of the constituent parts of the magnetic flux-concentrating means, such as the multipartite magnet yoke, are in the form of stamped-and-bent parts, it is necessary to manufacture these components in a highly complex manner in a plurality of production steps.